The invention pertains to visual displays and more particularly to twisting-ball displays, such as gyricon displays and the like.
Gyricon displays, also known by other names such as electrical twisting-ball displays or rotary ball displays, were first developed over twenty years ago. See U.S. Pat. No. 4,126,854 and No. 4,143,103, incorporated by reference hereinabove.
An exemplary gyricon display 10 is shown in side view in FIG. 1A (PRIOR ART). fnBichromal bails 1 are disposed in an elastomer substrate 2 that is swelled by a dielectric fluid creating cavities 3 in which the balls 1 are free to rotate. The balls 1 are electrically dipolar in the presence of the fluid and so are subject to rotation upon application of an electric field, as by matrixaddressarle electrodes 4a, 4b. The electrode 4a closest to upper surface 5 is preferably transparent. An observer at I sees an image formed by the black and white pattern of the balls 1 as rotated to expose their black or white faces (hemispheres) to the upper surface 5 of substrate 2.
A single one of bichromal balls 1, with black and white hemispheres 1a and 1b, is shown in FIG. 1B (PRIOR ART).
Gyricon displays have numerous advantages over conventional electrically addressable visual displays, such as LCD and CRT displays. In particular, they are suitable for viewing in ambient light, retain an image indefinitely in the absence of an applied electric field, and can be made lightweight, flexible, foldable, and with many other familiar and useful characteristics of ordinary writing paper. Thus, at least in principle, they are suitable both for display applications and for so-called electric paper or interactive paper applications, in which they serve as an electrically addressable, reuseable (and thus environmentally friendly) substitute for ordinary paper. For further a dvantages of the gyricon, see U.S. Pat. No. 5,389,945, incorporated by reference hereinabove.
Known gyricon displays employ spherical particles (e.g., bichromal balls) as their fundamental display elements. There are good reasons for using spherical particles. In particular:
Spherical bichromal balls can be readily manufactured by a number of techniques. See the '098 and '594 patents, incorporated by reference hereinabove, in this regard. PA1 Spheres are symmetrical in three dimensions. This means that fabrication of a gyricon display sheet fro m spherical particles is straighforward. It is only necessary to disperse the balls throughout an elastomer substrate, which is then swelled with dielectric fluid to form spherical cavities around the balls. The spherical balls can be placed anywhere within the substrate, and at any orientation with respect to each other and with respect to the substrate surface. There is no need to align the balls with one another or with the substrate surface. Once in place, a ball is free to rotate about any axis within its cavity.
Indeed, there would seem to be no reason to consider using anything other than spherical particles as the rotational elements of gyricon displays.
And so, nobody has-until now.